1. Field of Invention
This invention generally relates to an improved vented nursing bottle, specifically the incorporation of a leak prevention feature into the bottle design.
2. Prior Art
Nursing bottles have been used for many years to feed babies, as a convenient alternative to breast feeding. This alternate method eliminates the discomfort often associated with breast feeding and allows care givers other than the maternal parent to perform this feeding. Moreover, the amount fed to the baby using this alternative can be accurately monitored.
Despite its numerous advantages however, there are several disadvantages. One significant disadvantage is the difficulty associated with dispensing the liquid from the bottle. As liquid is dispensed, a partial vacuum forms in the bottle, making further dispensing of liquid more difficult. Many prior art designs have sought to eliminate this disadvantage, with limited success. These prior art designs can be broadly categorized into two types: variable volume designs and vented designs. These are discussed in more detail in the paragraphs below.
A variable volume bottle design is one in which the volume of the container diminishes as the liquid is dispensed. One example of this design is disclosed in U.S. Pat. No. 4,880,125. As indicated therein, the design utilizes a collapsible bag set inside a rigid container, and replacement of the container bottom with a plunger which is depressed to reduce the effective bag volume as the liquid is dispensed. There are a number of weaknesses in this design however. First, inadvertent application of excess force to the plunger could result in dispensing liquid to the baby at a rate which exceeds the baby's consumption. This could cause the baby to gag or could result in spillage. In addition, collapsible liners are, by necessity, fragile and must be replaced frequently, making their use expensive. Also, handling and use of this design is difficult due to its cumbersome shape when assembled.
Another variable volume bottle design is disclosed in U.S. Pat. No. 6,616,000. As indicated therein, that design also incorporates a collapsible liner which must be replaced frequently. In addition, the liner assumes an irregular shape as it collapses during use, making it difficult to determine the quantity of liquid consumed by the baby.
Many vented bottle designs have been developed in the prior art to try to reduce or eliminate the development of a partial vacuum in the bottle during feeding. One example is disclosed in U.S. Pat. No. 6,742,665. As indicated therein, the venting apparatus consists of a spring loaded valve which is opened to allow air to enter the bottle. There are weaknesses associated with this design as well. These types of bottles are prone to leakage if foreign material becomes lodged in the valve seal, or if the valve is inadvertently opened when the bottle is not sufficiently inverted. In addition, use of a spring mechanism leads to additional expense in manufacturing.
Another vented bottle design is disclosed in U.S. Pat. No. 5,779,071. As indicated therein, venting apparatus is incorporated into the design and the geometry of this apparatus is intended to vent the bottle, yet not allow leakage through the vent path. However, this design is prone to significant leakage under certain conditions, as illustrated in FIGS. 1 through 6. Referring to FIGS. 1 and 2, this prior art design consists of a container 100, a vent unit 200, a nipple 300, and a collar 400. The vent unit 200 consists of a vent insert 210 and a reservoir tube 220. The container has a marking 103 which prescribes the maximum fill level of the container. FIG. 3 illustrates a cross section of the assembled prior art bottle, after being filled with liquid to the prescribed level and then rotated into a substantially horizontal orientation. In this figure, the light shading represents a liquid inside the container (container liquid) 500, and the dark shading represents a liquid inside the reservoir tube (reservoir liquid) 600. As illustrated in FIGS. 4 and 5, significant leakage can occur if pressure is applied to the nipple 300 while the bottle is in the horizontal position. This application of pressure is most often due to the baby chewing on the nipple. Referring to FIG. 4, pressure applied to the nipple 300 causes the container liquid 500 to be forced into the vent unit 200 and results in accumulation of additional reservoir liquid 601. Referring to FIG. 5, as pressure on the nipple 300 is relieved, air 602 is drawn out of the vent unit 200. Referring to FIG. 6, as pressure is then reapplied, additional liquid is forced into the vent unit 200. When the liquid level inside the vent unit 200 reaches the center of a vent insert 210, it will leak out of the bottle through the vent insert.
The weakness in prior art design disclosed in U.S. Pat. No. 5,779,071 is recognized in published application US 2005/0258124 A1. As indicated therein, the weakness is addressed by changing the shape of the bottle and limiting the quantity of liquid to be contained therein such that the vent insert is never submerged. This new design has a number of disadvantages however. First, the oversized shape of the bottle will be difficult for a baby to hold. Second, the design significantly limits the quantity of liquid which can be placed in each bottle, potentially resulting in the need to use multiple bottles to administer an adequate feeding.
Another prior art design of this type is disclosed in U.S. Pat. No. 5,570,796. This design also utilizes a reservoir tube and vent insert, but must be oriented with the reservoir tube and vent insert facing upward to prevent leakage.